Abstract 4368: USP36 SUMOylates EXOSC10 and Las1L to promotes their function in rRNA processing

Abstract

Abstract Eukaryotic ribosome biogenesis is a highly regulated multistep process to generate ribosomes, including transcription of pre-ribosomal RNA, rRNA processing, ribosome subunit assembly and export. Dysregulation of ribosome biogenesis is associated with various human diseases, including ribosomopathies and cancer. Therefore, it is crucial to understand how ribosome biogenesis is regulated during normal cell homeostasis and how it is deregulated in human diseases. Here, we report that the ubiquitin-specific protease USP36 acts as a novel SUMO ligase to promote nucleolar protein SUMOylation. Using affinity purification, we found that USP36 associates with a large number of nucleolar and ribosome biogenesis-related proteins, including all 10 components of the nucleolar RNA exosome complex, EXOSC1 to EXOSC10, as well as the Las1L-Nol9 endonuclease-kinase complex. We showed that USP36 interacts with the RNA exosome through EXOSC10 and SUMOylates ECOSC10 at Lys 583. Mutating K583 impaired the binding of EXOSC10 to pre-rRNAs and the K583R mutant failed to rescue the defects in rRNA processing and cell growth inhibition caused by knockdown of endogenous EXOSC10. Likewise, USP36 interacts with the Las1L-Nol9 complex and promotes Las1L SUMOylation at K565. In addition, USP36 deubiquitinates Las1L and Nol9 and regulates their protein stability. Mutating K565 does not affect the levels of Las1L and the formation of the Las1L-Nol9 endonuclease-kinase complex. However, induced expression of a K565R mutant of Las1L failed to rescue the defects in rRNA processing and cell growth inhibition caused by knockdown of endogenous Las1L. Together, these results suggest that USP36 plays an important role in regulating ribosome biogenesis by post-translationally regulating the function of RNA exosome and Las1L-Nol9 complexes. Citation Format: Mushui Dai, Yanping Li, Yunhan Yang, Xiao-Xin Sun. USP36 SUMOylates EXOSC10 and Las1L to promotes their function in rRNA processing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4368.